Cored arc-lamp electrode.



C. C. WALLACE.

CORED ARC LAMP ELECTRODE.

APPLICATION EILED JUNE 5, I915.

Patent-ed May 2,1916.

Inventor Curts C.Wall

CURTIS C. WALLACE, 0F SCHJENJECTAIDY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPOTION OF NEW YORK.

CORED ARC-LAMP ELECTRODE.

ari.

Specification of Letters Patent.

Patented May a, rare.

Application filed June 5, 1915. Serial No. 32,410.

To all whom 'it may concern:

lie it known that I, Cun'rls C. WALLAQE, a citizen of the United States, residin at Schenectady. county of Schenectady, btate of New York. have invented certain new and useful Improvements in Cored Arc-Lamp Electrodes, of which the following is 'a specification.

My invention has reference to are lamp electrodes and the process of making the same, the electrodes being composed mainly of a carbon rod having a core containing a high percentage of mineral matters. Such electrodes are known as cored electrodes and are largely used in arc lamps for searchlights. mainly as the anodes of such are lamps; but they are also applicable for use and are used in other kinds of flaming arc lamps. Electrodes of this character have heretofore been made by forming a carbon rod with a central bore, squirting the plastic mass of which the core is to be composed into the bore, and then drying the squirted core at a moderate temperature. Cored carbons thus made were found to operate fairly well with a moderate current, between ten and fifteen amperes; but when these electrodes are used at a high current density, such as is employed in arc'lamps for searchlights, these electrodes develop certain defects.

In Searchlight arc lamps it is not uncommon to use anodes as small as three-quarters of an inch in diameter, with a current from one hundred and fifty to two hundred amperes. The cores of the electrodes made as heretofore indicated are invariably less dense than the main body; they are porous, and in the process of drying they shrink away from the walls of the bore which they are designed to fill, and are, therefore, practically loose within the bore, although not generally throughout their whole length. The consequence of this is that when these electrodes are used with the high current density suitable for Searchlight work the cores consume faster than the main body and the arc plays variably upon the core and upon the main body, and thus becomes unsteady and its luminosity varies. In addition thereto, it freqently happens with such electrodes that during operation portions of the core, of a length of from two to four centimeters, are forcibly ejected, the ejected portions striking the refleccontribute to'the arc and to the crater the mineral vapors which it is designed to furnish. I overcome these difficulties by making the electrodes so as to give to the core any desired and uniform density; the cores are made separately and are then inserted and cemented into the bore. All this is more fully explained by the following detailed description with reference to the accompanying drawing, in which Figure 1 shows .an axial section of an electrode made in accordance with my invention, and Fig. 2 shows a like section of an electrode at the stage when its parts are being assembled.-

The principal feature of the new electrode is that the core is made separately from the main body of the electrode, finished completely as if it were an independent electrode. The material which is designed to compose the core is mixed with a sufficient amount of a suitable agglutinant to make a plastic mass, which is molded to the shape which it is to have when finishedfi it is then dried at a moderate temperature of about 100 C., and is then baked at a high temperature, as is usual in electrode manufacture. The mainobody of the electrode is made in the same manner, but is formed with an axial bore, slightly greater in diameter than the core. The core is then coated with a suitable cement and is inserted into the axial bore of the main body and the cement is allowed to set.

As regards the materials to be employed there is a wide range of choice. For the highest grade of electrodes the main body or mantle 1 is composed of lampblack mixed with a carbonizable agglutinant, such as tar or sugar solution. Other forms of carbon and other agglutinants may be used, as is well known to those skilled in the art. This mass is formed into rods with an axial bore 2 in the usual and well known manner; it is then dried and baked as usual, but with particular precautions to prevent warping. The core 3 is composed mainly of between sixty to forty per cent. of carbon and between forty to sixty per cent. of mineral matters and a suitable carbonizable binder curs with my improved electrode.

to make the mixture plastic. The choice of the minerals depends upon the color and luminous intensity of the are desired. I may say, however, that fora White arc cerium fluorid and lanthanum fluorid in about the proportion of two to one has been found very effective. In particular the residue of monazite sand after the thorium which it contains has been extracted has been used. This residue is composed of cerium, lanthanum, neodymium, praseodymium, samarium, yttrium, and some phosphoric acid. The phosphoric acid is undesirable and is removed and the remainder is converted into acomplex fluorid. However, as heretofore stated, other materials may be used for the composition of the core. The core material, after it has been made plastic, is molded into a rod which is then dried and baked, and particular care is observed to prevent warping. The diameter of the rod must be so gaged that when dry it can be inserted with barely any friction into the bore of the main body of the electrode. The rod is then coated with an aqueous solution 4 of otash water glass and is then inserted into the bore of the main body, as indicated in .Fig. 2. The whole electrode is then subjected to a moderate heat to evaporate the solvent of the water glass.

By separately molding, squirting, pressing, drying, and baking the core, the latter can be made of uniform density and as dense as is desired, and by cementing it in place it does not become loose at any part of its length, and in operation it consumes, except at the beginning when the crater is being formed, at the same rate as the main body of the electrode. The ejection of pieces of the core hereinbefore described as occurring with ordinary electrodes never 0c- Electrodes thus made, about three-quarters of I an inch in diameter, have been used as anodes for Searchlight arc lamps, with from one hundred and fifty to two hundred amperes,

with excellent results.

vWhat I claim as new and desire to secure by Letters Patent of the United States, is

1. The process of making arc lamp carbon electrodes, which consists in molding the main body or mantle of the electrode with an axial bore and baking the same, molding and baking a mineralized electrode core, and then fitting and cementing the core into the axial bore of the main body.

2. The process of making cored are lamp carbon electrodes, which consists in moldin the main body or mantle of the electrode with an axial bore and baking the same, molding and baking the core for the electrodes separately, and then cementing the core into the axial bore with potassium water glass.

3. An arc lamp carbon'electrode having a separately baked mineralized core cemented in place.-

4. An arc lamp electrode, composed of a baked main body or mantle, principally of carbon, having an axial. bore, and a separately baked core composed of carbon and light-giving mineral matters fitting and cemented into the bore.

5. An arc lamp electrode, composed of a baked main body or mantle having an axial bore, a baked core composed of carbon and light-giving mineral matters fitted into the bore, and a film of potassium water glass connecting the core with the walls of the bore.

In witness whereof, I have hereunto set my hand this 4th day of June, 1915.

CURTIS C. WALLACE. 

